Preheat the oven to 400F with a rack in top third.
To assemble the lasagna combine the tomatoes, olive oil, salt, garlic, and red pepper flakes in a bowl and give a good stir.
Spoon 3/4 cup of the sauce into the bottom of a 8 x 12-inch (or larger) oven-proof baking dish. Sprinkle generously with lemon zest, and cover with a layer of pasta, giving the pasta strips a quick dunk in cold water before using - (please see note below if using no-boil noodles*).
Spoon another thin layer of tomato sauce, sprinkle with a few tablespoons of the lentils, the olives (if using), and cover with another layer of pasta. Repeat with more layers ending with a generous amount of tomato sauce on top. Finish with the mozzarella cheese on top (or see headnotes for vegan version).
Bake for thirty minutes, or until the cheese gets nicely golden.
*If using no-boil noodles, there's no need to dunk in water before assembling. Also, please cover the lasagna with foil and bake until pasta is tender - 30-35 minutes.
** Variation: Stir 1 1/2 teaspoons of your favorite curry powder and juice of 1/2 an orange into the tomato sauce.